JPS6128606B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing synthetic crystalline zeolites having an effective pore size of about 4 to 10 Å in a form that is substantially useful in adsorption processes.

Zeolite-type or crystalline aluminosilicate microselective adsorbents have a three-dimensional structure of silica, alumina, and tetrahedrons. This zeolite structure is characterized by a repeating three-dimensional network of large open aluminosilicate cages, connected by small uniform openings and pores. Some of these microselective adsorbents have been synthesized from sodium silicate and sodium aluminate. After synthesis, these large voids are filled with water. This water can be expelled by heating without destroying the cage. When dehydrated, these voids can readsorb large amounts of water or other vapors at low partial pressures. Because of this homogeneous structure, the pore openings connected to the aluminosilicate voids, these zeolites exhibit the unique property of excluding large molecules from the voids and allowing small molecules to pass through and be adsorbed. They thereby act as microselective adsorbents of molecules according to their size and shape.

Since the zeolite is removed from the manufacturing process as a fine powder, it is necessary to form the zeolite into a nodular structure that can be packed into a solid bed to adsorb gases or liquids from the stream. be. This is usually done by bonding the zeolite with a clay-like material.
However, a disadvantage of such a method is that the clay is inert and therefore 15-20% of the bed (depending on the percentage of clay used as binder) is inert. .

U.S. Pat. No. 3,119,659 to Taggert discloses a method for making so-called binderless sieves in which clay is converted to zeolite with a subsequent treatment to convert the clayey binder to zeolite. There is. The method includes a crystallization step in which the nodules are heated in a sodium hydroxide solution bath to convert the clay binder to zeolite.

This application method involves blending clay with type A or type X zeolite and adding sufficient amount of sodium hydroxide solution to form beads.
Manufactures type molecular sieves. If desired, the center may be added to a mixture of Type A or Type X zeolite, sodium hydroxide and clay. The mixture is then fired in a conventional kiln at a temperature of 93-316°C (200-600°). The product before firing is 30
It contains 45% to 45% water, and the water content decreases to 1 to 5% by drying and firing.

This method is an improvement on Tazgart's method in that it does not require an aging step. This law is 93
The clay binder is dried and converted to zeolite at temperatures between 200 and 600°C. The temperature is substantially higher than the crystallization temperature of Tatzgart and other processes for producing seamless molecular sieves. Additionally, crystallization is effected by using the water present in the beads as they form. And it is not necessary to carry out the crystallization in sodium hydroxide solution or under pressurized conditions.

The first step of the method is to mix the clay and the type A or type X zeolitic aluminosilicate.
The amount of clay present is about 10 to 30%, preferably 20%
It is. The method of making Type A or Type X zeolites is not part of this invention. It has been described in several issued patents. Very briefly, the method involves preparing a sodium aluminate solution from sodium hydroxide and trihydrated alumina, adding diluted sodium silicate to the desired concentration, and, if desired, adding core centers. It consists of Then add this mixture to approx.
Heat at a temperature of 100-125°C for a sufficient time to complete crystallization. Separate and wash the product;
If it is desired to convert the zeolite to the calcium form or other forms, an exchange reaction with calcium chloride or other salts is carried out. The product is then dried and stored.

The next step in our method is to blend the clay (metakaolin) and type A or type X zeolite and add a sufficient amount of sodium hydroxide. Sodium hydroxide is added to the zeolite and clay mixture blend at a concentration of 10 to 25 weight percent. This amount of sodium hydroxide feed corresponds to about 90 to 120% of the theoretical amount required to convert all of the metakaolin clay binder to zeolite. If desired, nuclear centers may be added to this mixture. The mixture is then formed into granules of a desired diameter. This step of the method is conventional and may require granulation and separation of the granules depending on particle size. Preferably, the agglomerate has a moisture content of about 30 to 40% after its shaping. This moisture originates from the sodium hydroxide solution added in the molding process. The granules are then dried in a rotary kiln or other conventional type of calcination equipment at temperatures of 93 to 316°C (200 to 600°C), simultaneously converting the metakaolin to zeolite, and then drying at 204 to 649°C (200 to 600°C). 400 to 1200
〓) Bake at a temperature of 〓). By selecting the drying and calcination temperatures within the above ranges, granules are obtained that have the physical strength and reactivity properties necessary to make a satisfactory absorbent. If the temperature is too low or too high, metakaolin will not crystallize to form zeolite. Furthermore, if the initial moisture content of the granules is too low, metakaolin will have difficulty crystallizing to form zeolite, and if the moisture content is too high, another drying step is required before crystallization. Unless done otherwise, the particulates tend to separate during the manufacturing process.
Therefore, it is preferable that the water content before drying is 30 to 45% by weight. During this drying the moisture content is reduced to about 10-20% and by calcination to about 1-5%, preferably about 3%. The final product is approximately 95 to
It is a hard, granular product containing type A or type X zeolite with 100% type A binder and suitable for use in adsorption processes.

Our invention is illustrated by the following specific but non-limiting examples.

Example 1 This example shows a method for producing seamless zeolite aggregates according to the present invention in a plant.

Sodium type A zeolite 1360Kg (3000
lbs) and 272 Kg (600 lbs) of metakaolin are blended using conventional mixing methods. Sodium hydroxide
A total of 118 kg (260 lbs) (120% of the theoretical amount required to convert metakaolin to type A zeolite) was added as a diluted solution in about 17 weight percent sodium hydroxide. This amount is metakaolin 45.3Kg
19.5Kg of 100% Sodium Hydroxide per (100 lbs)
(43 lbs). The blend is then mixed into a thin paste and the mixture has a particle size of about 4 to 8.
Approximately 434 Kg (960 lbs) of blended powder was added to the paste to form it into mesh granules. This addition reduces the amount of caustic that converts clay to zeolite to 95% of the theoretical amount.

Next, the blended granules are applied to a granulator, and the
Those that passed the mesh screen were selected for the next step in the method. In the next step of our method, the granular zeolite was formed into nodules. The moisture content (TV) of the granules was approximately 35% by weight. The granules were then crystallized by passing through a rotary kiln at a temperature of 93-316°C (200-600°C). No external steam was added during drying. The granules are placed in a dryer for 30 to 30 minutes.
It was kept for 60 minutes. passing the nodules through a second pass
The product was activated by passing it through a calciner operating at a temperature of 204-649°C (400-1200°) with a residence time of 30-60 minutes. The product (8-12 mesh beads) has the following properties: Total evaporation (TV) determined by weight loss on heating to 954°C (1750〓) 1.63; breaking strength Kg 4.44 (lbs 9.8); Density Kg/m ³ 672 (lbs/ft ³
42); Moisture adsorption amount at 10% relative humidity 23.17; 5%
Slurry PH11.37.

Example 2 A product was made using similar concentrations of reaction reagents as in Example 1. In this operation, crystallization was carried out in a calciner operating at about 149-316°C (300-600°C) and kept in the calciner for 30-40 minutes.
In the previous operation, the water vapor generated by the liquid in the granules was sufficient to complete the crystallization to convert metakaolin to Type A zeolite.
Activation of nodules is approximately 204 to 593 by the second pass.
30°C through a firing furnace at a temperature of 400 to 1100°C.
It was completed in a residence time of 40 minutes. Product (8-
12 mesh beads) were essentially type A zeolites and had the following properties. TV1.55; Average breaking strength Kg4.53 (lbs10.0); Density Kg/m ³ 688 (lbs/
^ft3 43); Moisture adsorption amount at 10% relative humidity 22.43; 5
% slurry nodules PH11.36.

Example 3 Firing in a rotary furnace at 149-316℃
(300 to 600〓)
The same amounts of reaction reagents were used and the same steps were followed in this example, except that the reactants were heated in the kiln for minutes. As in the previous operation, the water vapor generated by evaporation from the granules was sufficient to crystallize metakaolin into a product. The product was activated in a second pass through a calciner operating at 204-593°C (400-1100°). 30 to 40 nodules
This temperature was maintained for minutes. Removed product (8-12
The mesh beads were essentially 100% type A zeolite and had the following properties.

TV 1.58 Average breaking strength, Kg4.48 (lbs9.9) Density, Kg/m ³ 685 (lbs/ft ³ 42.8) Moisture adsorption, 10% relative humidity 23.06 PH of 5% slurry 11.42

Claims (1)

[Claims] 1. Powdered zeolite is mixed with metakaolin, sodium hydroxide, and water in amounts necessary to produce additional zeolite, and the resulting mixture is shaped to form granules containing reactive zeolite. a method of producing shaped zeolite granules comprising: (a) heating the moist shaped granules to 93 to 316°C;
(b) heating the granules at a temperature of 204-649°C (400-600°C) for 15-60 minutes to reduce its moisture content and simultaneously convert the metakaolin to zeolite;
A method characterized by firing at a temperature of 1200㎓ for 15 to 60 minutes. 2. The method of claim 1, wherein the calcined granules contain 95 to 100% zeolite. 3. The method of claim 1, wherein the powdered zeolite is selected from the group consisting of A-type zeolite, X-type zeolite, Y-type zeolite, and mixtures thereof. 4. The method according to claim 1, wherein the granules subjected to heating in step (a) contain 10 to 30% by weight of metakaolin. 5. The method according to claim 1, wherein the heating step (a) is performed in an atmosphere containing water vapor. 6. The method according to claim 1, wherein the firing step is performed under atmospheric pressure. 7. The method according to claim 1, wherein the firing is performed in the presence of air. 8. The method of claim 1, wherein the sodium hydroxide contained in the shaped granules is present as a 10 to 30 weight percent solution.